The invention relates to a method for operating a fuel supply system for an internal combustion engine, especially of a motor vehicle wherein the fuel is pumped by a pump into a pressure store and is injected directly into the engine via injection valves. Furthermore, the invention relates to a fuel supply system for an internal combustion engine, especially of a motor vehicle having a pressure store and a pump with which fuel can be supplied to the pressure store and having injection valves with which fuel can be injected directly into the engine.
Ever higher requirements are imposed on an internal combustion engine such as of a motor vehicle with respect to a reduction of the fuel consumption and the generated exhaust gases while simultaneously increasing the desired power. For this purpose, modern engines are provided with a fuel supply system in which the supply of fuel into the combustion chamber of the engine is controlled (open loop and/or closed loop) electronically, especially by a computer-supported control apparatus.
In the so-called gasoline direct injection, it is necessary that the fuel is injected into the combustion chamber under pressure. For this purpose, a pressure store is provided into which the fuel is pumped by a pump and is placed under a high pressure. From there, the fuel is injected into the combustion chambers of the engine via injection valves.
When starting the internal combustion engine, the above-mentioned high pressure is mostly not available or is at least not immediately available. The starting of the engine must therefore be separately controlled (open loop and/or closed loop). In this context, the already mentioned peripheral conditions, such as reduced toxic substance discharge, are to be satisfied.
It is an object of the invention to provide a method for operating a fuel supply system for an internal combustion engine with which a starting of the engine as optimal as possible can be carried out.
This object is achieved in a method and/or a fuel supply system of the type mentioned initially herein in accordance with the invention in that a pressure, which is adequate for the injection, is generated in the pressure store by the pump within a short time duration, especially within a few revolutions of the engine.
In this way, it is possible that no complex controls (open loop and/or closed loop) are required for the starting of the engine. In lieu thereof, the engine can be controlled (open loop and/or closed loop) essentially immediately in correspondence to its normal operation. The invention therefore makes possible a starting of the engine under conditions which correspond to the normal operation of the engine.
In an advantageous further embodiment of the invention, the adequate pressure is generated within a few revolutions after the start of the engine. In this way, the starting of the engine is further improved by means of the control (open loop and/or closed loop) in correspondence to the normal operation.
In a first advantageous embodiment of the invention, the pump is coupled to the engine and the engine is started at an rpm in the region of the idle rpm. For this purpose, the starter is preferably configured as a so-called starter-generator. Because the idle rpm is reached rapidly, the pressure, which is required for the normal operation, is almost immediately available in the pressure store.
In a second advantageous embodiment of the invention, an electrical pump is used for generating the pressure. This electrical pump can preferably be switched on together with the ignition and therefore preferably in advance of the starter. In this way, the pressure in the pressure store, which is required for the normal operation, can be built up by the electrical pump up to the actual starting operation.
Of special significance is the realization of the method of the invention in the form of a control element which is provided for a control apparatus of an internal combustion engine, especially of a motor vehicle. A program is stored on the control element which can be run on a computing apparatus, especially on a microprocessor, and is suitable for carrying out the method of the invention. In this case, the invention is realized by a program stored on the control element so that this control element, which is provided with the program, defines the invention in the same manner as the method for which the program is suitable for carrying out. As a control element, especially an electrical storage medium can be used, for example, a read-only-memory.